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Use a flag to indicate when the circular queue is fully populated and stable.

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Raymond Hettinger 2012-04-30 20:48:55 -07:00
parent 417c3848d5
commit 018b4fbb9b
1 changed files with 12 additions and 9 deletions
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21
Lib/functools.py
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@ -176,6 +176,7 @@ def lru_cache(maxsize=100, typed=False):
cache = {} cache = {}
hits = misses = currsize = 0 hits = misses = currsize = 0
full = False
cache_get = cache.get # bound method to lookup a key or return None cache_get = cache.get # bound method to lookup a key or return None
lock = Lock() # because linkedlist updates aren't threadsafe lock = Lock() # because linkedlist updates aren't threadsafe
root = [] # root of the circular doubly linked list root = [] # root of the circular doubly linked list
@ -224,7 +225,7 @@ def lru_cache(maxsize=100, typed=False):
def wrapper(*args, **kwds): def wrapper(*args, **kwds):
# size limited caching that tracks accesses by recency # size limited caching that tracks accesses by recency
nonlocal root, hits, misses, currsize nonlocal root, hits, misses, currsize, full
key = make_key(args, kwds, typed) if kwds or typed else args key = make_key(args, kwds, typed) if kwds or typed else args
with lock: with lock:
link = cache_get(key) link = cache_get(key)
@ -247,13 +248,7 @@ def lru_cache(maxsize=100, typed=False):
# update is already done, we need only return the # update is already done, we need only return the
# computed result and update the count of misses. # computed result and update the count of misses.
pass pass
if currsize < maxsize: elif full:
# put result in a new link at the front of the queue
last = root[PREV]
link = [last, root, key, result]
cache[key] = last[NEXT] = root[PREV] = link
currsize += 1
else:
# use root to store the new key and result # use root to store the new key and result
root[KEY] = key root[KEY] = key
root[RESULT] = result root[RESULT] = result
@ -262,6 +257,13 @@ def lru_cache(maxsize=100, typed=False):
root = root[NEXT] root = root[NEXT]
del cache[root[KEY]] del cache[root[KEY]]
root[KEY] = root[RESULT] = None root[KEY] = root[RESULT] = None
else:
# put result in a new link at the front of the queue
last = root[PREV]
link = [last, root, key, result]
cache[key] = last[NEXT] = root[PREV] = link
currsize += 1
full = (currsize == maxsize)
misses += 1 misses += 1
return result return result
@ -272,11 +274,12 @@ def lru_cache(maxsize=100, typed=False):
def cache_clear(): def cache_clear():
"""Clear the cache and cache statistics""" """Clear the cache and cache statistics"""
nonlocal hits, misses, currsize nonlocal hits, misses, currsize, full
with lock: with lock:
cache.clear() cache.clear()
root[:] = [root, root, None, None] root[:] = [root, root, None, None]
hits = misses = currsize = 0 hits = misses = currsize = 0
full = False
wrapper.cache_info = cache_info wrapper.cache_info = cache_info
wrapper.cache_clear = cache_clear wrapper.cache_clear = cache_clear